Long term goals of this proposed study concerns the biochemical endocrinology of gonadotropins. The immediate objective is to determine which subunit of follitropin binds to the hormone receptor and identify and characterize the follitropin receptor in the following steps. 1) To prepare photoaffinity derivatives fo follitropin. 2) To test the binding activity and steroidogenesis of the follitropin derivatives. 3) To covalently label the hormone receptor with the follitropin derivatives. 4) To analyze photoaffinity labeled receptor-follitropin complexes by SDS-PAGE, gel permeation and centrifugation. 5) Characterize receptor components of the complexes by proteolytic digestions, immunoprecipitation.